Use sigaction(SA_NOCLDWAIT) for SIGCHLD handling
signal() semantics are pretty unclearly specified. For example, depending on OS kernel and libc, the handler may be returned to SIG_DFL (hence the inner call to read the signal handler). Moving to sigaction() means the behaviour is consistently defined. Using SA_NOCLDWAIT also allows us to avoid calling the non-reentrant function die() in the handler. Some addditional notes for archival purposes: * NRK pointed out errno of waitpid could also theoretically get clobbered. * The original patch was iterated on and modified by NRK and Hiltjo: * SIG_DFL was changed to SIG_IGN, this is required, atleast on older systems such as tested on Slackware 11. * signals are not blocked using sigprocmask, because in theory it would briefly for example also ignore a SIGTERM signal. It is OK if waitpid() is (in theory interrupted). POSIX reference: "Consequences of Process Termination": https://pubs.opengroup.org/onlinepubs/9699919799/functions/_Exit.html#tag_16_01_03_01
This commit is contained in:
parent
89f9905714
commit
712d6639ff
20
dwm.c
20
dwm.c
@ -205,7 +205,6 @@ static void setmfact(const Arg *arg);
|
|||||||
static void setup(void);
|
static void setup(void);
|
||||||
static void seturgent(Client *c, int urg);
|
static void seturgent(Client *c, int urg);
|
||||||
static void showhide(Client *c);
|
static void showhide(Client *c);
|
||||||
static void sigchld(int unused);
|
|
||||||
static void spawn(const Arg *arg);
|
static void spawn(const Arg *arg);
|
||||||
static void tag(const Arg *arg);
|
static void tag(const Arg *arg);
|
||||||
static void tagmon(const Arg *arg);
|
static void tagmon(const Arg *arg);
|
||||||
@ -1543,9 +1542,16 @@ setup(void)
|
|||||||
int i;
|
int i;
|
||||||
XSetWindowAttributes wa;
|
XSetWindowAttributes wa;
|
||||||
Atom utf8string;
|
Atom utf8string;
|
||||||
|
struct sigaction sa;
|
||||||
|
|
||||||
/* clean up any zombies immediately */
|
/* do not transform children into zombies when they terminate */
|
||||||
sigchld(0);
|
sigemptyset(&sa.sa_mask);
|
||||||
|
sa.sa_flags = SA_NOCLDSTOP | SA_NOCLDWAIT | SA_RESTART;
|
||||||
|
sa.sa_handler = SIG_IGN;
|
||||||
|
sigaction(SIGCHLD, &sa, NULL);
|
||||||
|
|
||||||
|
/* clean up any zombies (inherited from .xinitrc etc) immediately */
|
||||||
|
while (waitpid(-1, NULL, WNOHANG) > 0);
|
||||||
|
|
||||||
/* init screen */
|
/* init screen */
|
||||||
screen = DefaultScreen(dpy);
|
screen = DefaultScreen(dpy);
|
||||||
@ -1638,14 +1644,6 @@ showhide(Client *c)
|
|||||||
}
|
}
|
||||||
}
|
}
|
||||||
|
|
||||||
void
|
|
||||||
sigchld(int unused)
|
|
||||||
{
|
|
||||||
if (signal(SIGCHLD, sigchld) == SIG_ERR)
|
|
||||||
die("can't install SIGCHLD handler:");
|
|
||||||
while (0 < waitpid(-1, NULL, WNOHANG));
|
|
||||||
}
|
|
||||||
|
|
||||||
void
|
void
|
||||||
spawn(const Arg *arg)
|
spawn(const Arg *arg)
|
||||||
{
|
{
|
||||||
|
Loading…
Reference in New Issue
Block a user